Composition of electroplating bath for the electrodeposition of bright nickel

ABSTRACT

An aqueous, acid electroplating bath which contains as brightening agents the synergistic combination of N-(3sulfopropyl) pyridinium inner salt and an acetylenic alcoholethylene oxide adduct.

United States Patent Rosenberg et al.

[ 1 Jan. 21, 1975 COMPOSITION OF ELECTROPLATING BATH FOR THEELECTRODEPOSITION OF BRIGHT NICKEL Inventors: William E. Rosenberg,Strongsville;

William J. Saas, Fairview Park, both of Ohio Assignee: R. 0. Hull &Company, Inc.,

Cleveland, Ohio Filed: Apr. 26, 1974 Appl. No.: 464,558

U.S. Cl. 204/49 Int. Cl. C23b 5/08, C23b 5/46 Field of Search 204/49, 43T, 43 N, 43 P,

Primary Examiner-G. L. Kaplan Attorney, Agent, or FirmO1dham & OldhamC0.

[57] ABSTRACT An aqueous, acid electroplating bath which contains asbrightening agents the synergistic combination of N-(3-su1fopropy1)pyridinium inner salt and an acetylenic alcohol-ethylene oxide adduct.

8 Claims, No Drawings BACKGROUND OF THE INVENTION This invention relatesto an aqueous acid electroplating bath for producing extremely bright,level electrodeposits of nickel. The use of N-(3-sulfopropyl) pyridiniuminner salts as a bath additive is disclosed in US. Pat. No. 2,876,l77.It is used alone or in combination with diarylsulfimides. The depositsobtained using a bath containing this combination or the pyridiniuminner salt alone are level but only semibright. However, the deposit issomewhat brittle and if more brightener is added to achieve a higherdegree of brightness and leveling, the brittleness increases and thereis a definite darkening of the plate in low current density areas. Suchbrittleness and plate discoloration is totally unacceptable for suitableplating.

The use of acetylenic alcohol-ethylene oxide adducts is also known inthe electroplating industry and is disclosed in U.S. Pat. No. 3,140,988.They are used alone and in combination with allyl sulfonic acid, andaryl sulfonic amides and acids. US. Pat. No. 3,366,557 discloses similarcombinations and U.S. Pat. No. 3,11 1,466 discloses the combination ofcoumarin and ethylene oxide adducts of acetylenic alcohols.

However, in all three of these disclosures utilizing the acetylenicalcohol adducts at best only semibright and moderately levelelectrodeposits are obtained. Moreover. it has been found that byexcessively increasing the concentration of the brighteners in theelectroplating baths, electrodeposits exhibiting extremely highbrightness and leveling cannot be obtained.

These brightening systems, therefore are limited in at least thefollowing aspects:

1. The system using the pyridinium inner salt is limited in thatincreasing the concentration to achieve extremely high luster andleveling produces unacceptable, brittle and dark electrodeposits; and

2. The systems using the acetylenic alcohol adducts cannot produceelectrodeposits of extremely high brightness and leveling even at veryhigh concentrations in the electroplating bath.

SUMMARY OF THE INVENTION Accordingly, it is an object of the inventionto provide brightening agents which produce extremely bright, level andductile electrodeposits of nickel.

It is another object of the present invention to produce an extremelybright electrodeposit of nickel, as above, through the synergisticcombination of two groups of compounds, even in low current densityareas.

These and other objects of the present invention, together with theadvantages thereof over existing prior art compounds and methods whichwill become apparent from the following specification are accomplishedby the compounds and methods herein described and claimed.

In general, a plating bath for the electrodeposition of nickel.comprises, an aqueous acidic solution of at least one nickel salt and.as brightening agents, from 0.02 to about 0.5 grams/liter ofN-(3-sulfopropyl) pyridinium inner salt and from 0.005 to about0.2'grams/liter of an acetylenic alcohol-ethylene oxide adduct havingthe general formula where R, is hydrogen, hydroxymethyl, and2-hydroxyethoxymethyl and R is 2-hydroxyethoxymethyl.

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the concepts ofthe present invention, it has been found that the synergisticcombination of an N-(3-sulfopropyl) pyridinium inner salt and anacetylenic alcohol-ethylene oxide adduct produces both extremely brightand level electrodeposits of nickel at very low concentrations in anaqueous acidic nickel plating bath. Additionally, the electrodeposit isextremely ductile. The effect is truly synergistic in that the resultsobtained with this combination far exceed those of using the two typesof compounds separately and at brightener concentrations of only a smallfraction of previously required amounts.

The pyridinium inner salt of the present invention has the followingformula:

All-12011: AII:

This specific salt is generally not commercially available but may bereadily synthesized by the condensation of pyridine and propane sultone.

The aceylenic alcohol-ethylene oxide adducts of the present inventionare available in commerce and have the following general formula:

where R, is hydrogen, hydroxymethyl, and Z-hydroxyethoxymethyl, and R isZ-hydroxyethoxymethyl. The chemical structures of these compounds areset forth in Table I.

TABLE I 1. HOCH CH OCH C CCH OH 2. HOCH- CH OCH C CH 3. HOCH CH OCHC"CCH OCH CH OH The brighteners of this invention can readily be used inconjunction with other known conventional brighteners in generally smallor conventional amounts such as allyl sulfonic acid, aromatic sulfonicacids, and aromatic sulfonamides and sulfonimides; specific examplesinclude saccharin, dibenzenesulfonimide and naphthalene trisulfonicacid.

The pyridinium inner salt and acetylenic alcoholethylene oxide adductsof this invention are generally added as aqueous solutions, but they canbe added in concentrated form or dissolved in another suitable solventsuch as methanol or ethanol. A general range extends from 0.02 to about0.5 grams/liter of plating bath for the pyridinium inner salt and from0.005 to about 0.20 grams/liter of the plating bath for the acetylenicalcohol-ethylene oxide adduct. More specifically, the preferredconcentrations are about 0.05 to about 0.3 gms with roughly 0.18 gmsbeing an optimum amount of the' pyridinium inner salt and about 0.01 toabout 0.10 gms with roughly 0.03 gms being an optimum amount of theacetylenic alcohol-ethylene oxide adduct per liter of bath.

Continued pH 4.2 Temperature I4()F.

Table I shows the tests that were run in this bath under the abovementioned conditions to demonstrate the unique synergism between theN-(3-sulfopropyl) pyridinium inner salt and the ethylene oxide adductsof amount of time will, of course, vary depending upon m the acetylenicalcohols.

TABLE I] Test Brighteners Used Concentration Results in g/l 1 HC 5 cCHOCH CH OH 0.03 Very dull deposit 2 HC ii CCH OCH CH OH 0.15 Very dulldeposit 3 IAI%CHH CH OCH,C I CCH OCH C- 0.03 Very dull deposit 2 4 goci-ucl-uocu c i CCH,OCH,C- 0.15 Very dull deposit H 2 5N-(3-sulfopropyl) pyridinium 0.06 Very dull deposit inner salt 6N-(3-sulfopropyl) pyridinium 0.l8 Semibri ht and inner salt cloudyeposit 7 N-(3-sulfopropyl) pyridinium 0.48 Sembri ht but inner saltbrittle eposit and dark in low current density 8 HC CCH,OCH CH OH 0.03Semibright, very Soluble saccharin 3 little leveling 9 HOCH,CH OCH C CC-0.03 Semibright, very H OCH CH OH Soluble saccharin 3 little leveling l0HOCH,CH,OCH C CH OH 0.03 Semibright, very Soluble saccharin 3 littleleveling l l HC I CCH OCH CH,OH 0.03 Extremely bright,

N-(3-sulfopropyl) pyridinium 0. 18 excellent leveling, inner salt andbright in low and bright in low current density 12 II II%CHH CH OCH C IiCCH OCH C- 0.03 Extremely bright,

2 N-(3-sulfopropyl) pyridinium 0.l8 excellent leveling, inner salt andbright in low current density [3 HOCH,CH 0CH C n CCH OH 0.03 Extremelybright,

N( 3-sulfopropyl) pyridinium 0.l8 excellent leveling,

and bright in low current density 14 :(6CH CH,OCH C I CCH OCH c- 0.03Extremely bright,

H z N-(3-sulfopropyl) pyridinium 0. 18 excellent leveling inner salt andbright in low Soluble saccharin 3 current density Note: All test bathscontained 0.3 g Sodium Lauryl Sulfate/liter to prevent gas streaking andpitting. Generally, any suitable surfactant may be used. A suitablesurfactant is one that prevents gas streaking and pitting but does notinterfere with brightness of the electrodeposit.

INGREDIENT CONCENTRATION Nickel Sulfate 36 ozJgal Nickel Chloride l0ozJgal Boric Acid 6.5 o7./gal

As can be seen from the results of Table H, the ethylene oxide adductsof acetylenic alcohols and N-(3- sulfopropyl) pyridinium inner salt actsynergistically when both are added to an aqueous acid nickelelectroplating bath to produce extremely bright, level electrodepositsof nickel. When these compounds are added separately, even in largeamounts, only semi-bright, cloudy, and in some cases brittle depositsresult.

Having thus described this invention in such full, clear, concise andexact terms as to enable any person skilled in the art to which itpertains to make and use the same, and having set forth the best modecontemplated of carrying out this invention in accordance with thePatent Statutes, the subject matter which is regarded as being ourinvention is particularly pointed out and distinctly claimed in what isclaimed, it being understood that equivalents or substitutions for,parts of the above specifically described embodiment of the where R ishydrogen, hydroxymethyl. or Z-hydroxyethoxymethyl, and R isZ-hydroxyethoxymethyl.

2. A plating bath according to claim 1 including a suitable surfactantin an amount sufficient to prevent gas streaking and pitting.

3. A plating bath according to claim 2, including at least one compoundselected from the group consisting of allyl sulfonic acids, aromaticsulfonic acids, aromatic sulfonamides and aromatic sulfonimides in anamount sufficient to further enhance the nickel deposit brightness.

4. A plating bath according to claim 2, wherein there is also presentsaccahrin in an amount sufficient to prevent gas streaking and pitting.

5. A plating bath according to claim 2, wherein there is also presentdibenzenesulfonimide in an amount sufficient to prevent gas streakingand pitting.

6. A plating bath according to claim 2, wherein there is presentnaphthalene trisulfonic acid in an amount sufficient to prevent gasstreaking and pitting.

7. A plating bath according to claim 1, wherein the amount of said N-(3-sulfopropyl) pyridinium inner salt ranges from about 0.05 to about0.3g/l and the amount of said acetylenic alcohol-ethylene oxide adductranges from about 0.01 to about 0.lg/l.

8. A plating bath according to claim I, wherein the amount of saidN-(3-sulfopropyl) pyridinium inner salt is approximately 0.]8g/l and theamount of said acctylenic alcohol-ethylene oxide adduct is approximately0.03g/l.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 019Dated January 1975 Inventor) William E. Rosenberg and William J. Saas Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 5, line 9 delete "0.02" and, in its place, insert O.2.

Signed and Scaled this Tenth D a y Of September 1985 [SEAL] A nest:

DONALD J. QUIGG A nesting Officer Acting (Lommissioner of Patents andTrademarks Designate UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION PATENT NO. 362,019 DATED January. 21, 1975 INVENTOR(S)William E. Rosenberg and William J. Saas It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 5, line 8, after "N-(3-si1lfopropyl)" insert .pyridinium Signedand Scalcd this second Day of December1975 [SEAL] A ttest:

RUTH C. MASON C. MARSHALL DANN A nesting Offirtr (0mm issiuner ofPatnlsand Tmdemarks

2. A plating bath according to claim 1 including a suitable surfactantin an amount sufficient to prevent gas streaking and pitting.
 3. Aplating bath according to claim 2, including at least one compoundselected from the group consisting of allyl sulfonic acids, aromaticsulfonic acids, aromatic sulfonamides and aromatic sulfonimides in anamount sufficient to further enhance the nickel deposit brightness.
 4. Aplating bath according to claim 2, wherein there is also presentsaccahrin in an amount sufficient to prevent gas streaking and pitting.5. A plating bath according to claim 2, wherein there is also presentdibenzenesulfonimide in an amount sufficient to prevent gas streakingand pitting.
 6. A plating bath according to claim 2, wherein there ispresent naphthalene trisulfonic acid in an amount sufficient to preventgas streaking and pitting.
 7. A plating bath according to claim 1,wherein the amount of said N-(3-sulfopropyl) pyridinium inner saltranges from about 0.05 to about 0.3g/l and the amount of said acetylenicalcohol-ethylene oxide adduct ranges from about 0.01 to about 0.1g/l. 8.A plating bath according to claim 1, wherein the amount of saidN-(3-sulfopropyl) pyridinium inner salt is approximately 0.18g/l and theamount of said acctylenic alcohol-ethylene oxide adduct is approximately0.03g/l.